While a smoker is smoking an ignited cigarette, a burning cone of the ignited cigarette needs to be maintained, namely prevented from stopping burning also between the smoker's drawing-in actions, or so-called puffs. Thus, even if intervals between puffs are somewhat longer, the smoker can smoke the ignited cigarette repeatedly.
However, if the ignited cigarette falls onto a combustible object such as a floor due to the smoker's carelessness, free combustion of the ignited cigarette may cause burning of the combustible object. Hence in tobacco industry, development of a so-called low ignition propensity cigarette (hereinafter referred to simply as “cigarette”), namely a cigarette that can hold down the risk of ignition of a combustible object in the above-described situation is demanded.
In order to meet this demand, for example Japanese Unexamined Patent Publication No. hei 11-46744 and Japanese Unexamined Patent Publication No. hei 11-318416 have proposed cigarettes of this type. In the cigarette proposed in the former publication, a paper tube that wraps shred tobacco has a plurality of air barrier zones for reducing permeation of air. These air barrier zones are arranged in the longitudinal direction of the cigarette at predetermined intervals. When this cigarette is in free combustion and the burning cone of the cigarette reaches one of the air barrier zones, the air barrier zone reduces supply of air to the burning cone, and thereby stops burning of the burning cone. Thus, the risk of the ignited cigarette igniting another object is held down.
The paper tube of the cigarette proposed in the latter publication has heat conduction strips on its inner surface. The heat conduction strips extends in the axial direction of the paper tube. It is thought that when this cigarette is in free combustion, the heat conduction strip draws heat from the burning cone and thereby lowers the temperature of the burning cone. Thus, like the above-described air barrier zones, the heat conduction strip stops burning of the burning cone.
A cigarette disclosed in Japanese Unexamined Patent Publication No. hei 5-76335 can reduce sidestream smoke produced between puffs. Inside the paper tube, the cigarette has puff pockets containing shred tobacco, and inter-puff pockets containing materials other than tobacco. The puff pockets and inter-puff pockets are alternately arranged in the longitudinal direction of the cigarette. A fuse connects the puff pockets and the inter-puff pockets with one another, and thereby maintains smoldering between puffs. It is thought that also in this cigarette, the inter-puff pockets lower the temperature of the burning cone, so that the risk of the ignited cigarette igniting another object is held down.
However, any of the cigarettes disclosed in the above-mentioned publications contains additional elements other than the tobacco materials and paper. Those additional elements change the cigarettes' original aroma and flavor to a large degree when the cigarettes are smoked, although the cigarettes are articles of taste. Hence, smokers do not like cigarettes of the above-mentioned types. Also, the additional elements increase the cigarette production cost to a large degree.